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View Full Version : I need the Brain Trusts thoughts on this one.



nemick
11-24-2015, 04:38 PM
I posted previously about a clunking my car makes under acceleration. Only does it from a stop and only between 17-19 mph. No other issues, drives fine, shifts fine, no weirdness cruising or decelerating. It was suggested that it might be the driveshaft support or the forward rear diff mount. This clunk is quite rapid and not really metallic. Actually sounds like someone hitting under the car with a rubber dead blow hammer.

So, I removed the heat shield and inspected the driveshaft support. It looks perfect and there is very little movement of the driveshaft, maybe 1/4" whichever way I push it. No signs, of cracking, perishing or anything untoward, dry as a bone, so not soaked in oil or road grime.

Next I removed the forward rear diff mount. This shows it's getting a little old, but not torn, maybe a couple of minute cracks, no oil or other crap and under any other circumstance I wouldn't think it was worth replacing. Also, I have no idea how stiff this thing is supposed to be. It might be that it's a lot softer than a new one, I have no way of comparing. However, I can see witness marks, which appear fairly fresh where it has been making contact on it's own bracket and also the aluminum bracket that it bolts to. I will be replacing it with the Ecs version as it's currently on sale.

That said, what else could be going too soft and allowing the forces to be sending this diff mount bouncing? If I understand it correctly, the rear diff is mounted to the cross member and the cross member mounts to the subframe with two of it's own mounts. Theses "look" okay but I haven't removed them. Are there any other diff mounts that I'm missing?

Sorry this is so lengthy but I want to make sure I'm describing things properly.

Thanks

GOODBYNAAIR
11-24-2015, 04:42 PM
are all your motor and trans mounts good ? control arms should be something to look at too

nemick
11-24-2015, 05:28 PM
Motor and trans mounts are a couple of years old. Front control arms are three years old. Rear control arms are all original, but I can't find any untoward movement on them when trying to flex them with a pry bar.